[Dovecot] Disallow Deletion from Trash Folder

Hello:

I've been tasked with trying to find a way to keep users from ever "permanently" deleting emails. The users are running Thunderbird and are using the "Archive" option for when emails are deleted. However, they are still able to delete emails from the Archive folders... I'm wondering if there's any way that I can configure Dovecot to make sure that emails *never* get removed from the filesystem. I know it's probably kind of a bizarre request, but is there any way that Dovecot can help me out in this regard?

Thanks!

B. Rintoul